Resist composition and method for producing resist pattern

ABSTRACT

A resist composition of the present invention has (A1) a resin having a structural unit represented by the formula (I), (A2) a resin being insoluble or poorly soluble in alkali aqueous solution, but becoming soluble in an alkali aqueous solution by the action of an acid, (B) an acid generator and (D) a compound represented by the formula (II). 
     
       
         
         
             
             
         
       
     
     wherein R 1  represents a hydrogen atom or a methyl group; A 1  represents a C 1  to C 6  alkanediyl group; R 2  represents a C 1  to C 10  hydrocarbon group having a fluorine atom, R 3  and R 4  in each occurrence independently represent a C 1  to C 12  hydrocarbon group, a C 1  to C 6  alkoxyl group, a C 2  to C 7  acyl group, a C 2  to C 7  acyloxy group, a C 2  to C 7  alkoxycarbonyl group, a nitro group or a halogen atom; m′ and n′ independently represent an integer of 0 to 4.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to Japanese Application No. 2011-39458filed on Feb. 25, 2011. The entire disclosures of Japanese ApplicationNo. 2011-39458 is incorporated hereinto by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a resist composition and a method forproducing resist pattern.

2. Background Information

A resist composition which contains a resin having a polymer obtained bypolymerizing a compound represented by the formula (u-A) and a compoundrepresented by the formula (u-B), and a polymer obtained by polymerizinga compound represented by the formula (u-B), a compound represented bythe formula (u-C) and a compound represented by the formula (u-D); anacid generator; and a solvent, is described in Patent document ofJP-2010-197413A.

However, the pattern line edge roughness (LER) to be provided from theconventional resist composition may be not always satisfied with, andnumber of the defects of the resist pattern may quite increase.

SUMMARY OF THE INVENTION

The present invention provides following inventions of <1> to <6>.

<1> A resist composition having;

(A1) a resin having a structural unit represented by the formula

(A2) a resin being insoluble or poorly soluble in alkali aqueoussolution, but becoming soluble in an alkali aqueous solution by theaction of an acid,

(B) an acid generator and

(D) a compound represented by the formula (II),

wherein R¹ represents a hydrogen atom or a methyl group;

A¹ represents a C₁ to C₅ alkanediyl group;

R² represents a C₁ to C₁₀ hydrocarbon group having a fluorine atom.

wherein R³ and R⁴ in each occurrence independently represent a C₁ to C₁₂hydrocarbon group, a C₁ to C₆ alkoxyl group, a C₂ to C₇ acyl group, a C₂to C₇ acyloxy group, a C₂ to C₇ alkoxycarbonyl group, a nitro group or ahalogen atom;

m′ and n′ independently represent an integer of 0 to 4.

<2> The resist composition according to <1>, wherein R² in the formula(I) is a C₁ to C₆ fluorinated alkyl group.

<3> The resist composition according to <1> or <2>, wherein A¹ in theformula (I) is a C₂ to C₄ alkanediyl group.

<4> The resist composition according to any one of <1> to <3>, whereinA¹ in the formula (I) is an ethylene group.

<5> The resist composition according to any one of <1> to <4>, whichfurther comprises a solvent.

<6> A method for producing resist pattern comprising steps of;

(1) applying the resist composition any one of <1> to <5> onto asubstrate;

(2) drying the applied composition to form a composition layer;

(3) exposing the composition layer;

(4) heating the exposed composition layer, and

(5) developing the heated composition layer.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

“(Meth)acrylic monomer” means at least one monomer having a structure of“CH₂═CH—CO—” or “CH₂═C(CH₃)—CO—”, as well as “(meth)acrylate” and“(meth)acrylic acid” mean “at least one acrylate or methacrylate” and“at least one acrylic acid or methacrylic acid,” respectively.

<Resist Composition>

The resist composition of the present invention contains;

(A) a resin (hereinafter may be referred to as “resin (A)”), and

(B) an acid generator (hereinafter may be referred to as “acid generator(B)”) and

(D) a compound represented by the formula (II) (hereinafter may bereferred to as “compound (II)”).

Further, the present resist composition preferably contains a solvent(hereinafter may be referred to as “solvent (E)”), as needed.

<Resin (A)>

The resin (A) includes;

(A1) a resin having a structural unit represented by the formula (I),and

(A2) a resin being insoluble or poorly soluble in alkali aqueoussolution, but becoming soluble in an alkali aqueous solution by theaction of an acid.

Also, the resin (A) may contain a structural unit other than the resin(A1) and resin (A2).

<Resin (A1)>

The resin (A1) has a structural unit represented by the formula (I)(hereinafter may be referred to as “structural unit (I)”).

wherein R¹ represents a hydrogen atom or a methyl group;

A¹ represents a C₁ to C₆ alkanediyl group;

R² represents a C₁ to C₁₀ hydrocarbon group having a fluorine atom.

In the formula (I), examples of the alkanediyl group of A¹ include achain alkanediyl group such as methylene, ethylene, propane-1,3-diyl,propane-1,2-diyl, butane-1,4-diyl, pentane-1,5-diyl, hexane-1,6-diyl; abranched alkanediyl group such as 1-methylpropane-1,3-diyl,2-methylpropane-1,3-diyl, 2-methylpropane-1,2-diyl,1-mrthylbutane-1,4-diyl, 2-methylbutane-1,4-diyl groups.

The hydrocarbon group of R² may be any of an aliphatic hydrocarbongroup, an aromatic hydrocarbon group and a combination of two or moresuch groups. The aliphatic hydrocarbon group may be any of a chain andcyclic aliphatic hydrocarbon group, and a combination of two or moresuch groups. The aliphatic hydrocarbon group is preferably an alkylgroup and an alicyclic group.

Examples of the alkyl group include methyl, ethyl, n-propyl, iso-propyl,n-butyl, sec-butyl, tert-butyl, iso-butyl, n-pentyl, iso-pentyl,tert-pentyl, neo-pentyl, hexyl, octyl and 2-ethylhexyl groups.

The alicyclic hydrocarbon group may be either monocyclic or polycyclichydrocarbon group. Examples of the monocyclic alicyclic hydrocarbongroup include cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl,methylcyclohexyl, dimethylcyclohexyl, cycloheptyl, cyclooctyl andcyclodecyl groups. Examples of the polycyclic alicyclic hydrocarbongroup include decahydronaphtyl, adamantyl, 2-alkyladamantane-2-yl,1-(adamantane-1-yl)alkane-1-yl, norbornyl, methylnorbornyl and isobornylgroups.

The hydrocarbon group having a fluorine atom of R² is preferably analkyl group having a fluorine atom and an alicyclic hydrocarbon grouphaving a fluorine atom.

Examples of the alkyl group having a fluorine atom include a fluorinatedalkyl group such as difluoromethyl, trifluoromethyl, 1,1-difluoroethyl,2,2-difluoroethyl, 1,1,1-trifluoroethyl, 2,2,2-trifluoroethyl,perfluoroethyl, 1,1,2,2-tetrafluoropropyl, 1,1,1,2,2-pentafluoropropyl,1,1,2,2,3,3-hexafluoropropyl, perfluoroethylmethyl,1-(trifluoromethyl)-1,2,2,2-tetratrifluoroethyl, perfluoropropyl,1,1,2,2-tetrafluorobutyl, 1,1,2,2,3,3-hexafluorobutyl,1,1,2,2,3,3,4,4-octafluorobutyl, perfluorobutyl,1,1-bis(trifluoro)methyl-2,2,2-trifluoroethyl, 2-(perfluoropropyl)ethyl,1,1,2,2,3,3,4,4-octafluoropentyl, 1,1,1,2,2,3,3,4,4-nonafluoropentyl,perfluoropentyl, 1,1,2,2,3,3,4,4,5,5-decafluoropentyl,1,1-bis(trifluoromethyl)-2,2,3,3,3-pentafluoropropyl,1,1,1,2,2,3,3,4,4-nonafluoropentyl, perfluoropentyl,2-(perfluorobutyl)ethyl, 1,1,2,2,3,3,4,4,5,5-decafluorohexyl,1,1,2,2,3,3,4,4,5,5,6,6-dodecafluorohexyl, perfluoropentylmethyl,perfluorohexyl, perfluoroheptyl and perfluorooctyl groups.

Examples of the alicyclic haydrocarbon group having a fluorine atominclude a fluorinated cycloalkyl group such as perfluoricyclohexyl andperfluoroadamanthyl groups.

A¹ in the formula (I) is preferably a C₂ to C₄ alkanediyl group, andmore preferably an ethylene group.

R² is preferably a fluorinated alkyl group, and more preferably a C₁ toC₆ fluorinated alkyl group.

Specific examples of the structural units (I) include as follows.

Also, examples of the structural units (I) include structural units inwhich a methyl group corresponding to R¹ in the structural unitsrepresented by the above is replaced by a hydrogen atom.

The structural unit (I) is derived from a compound represented by theformula (I′), hereinafter may be referred to as “compound (I′)”.

wherein A¹, R¹ and R² have the same definition of the above.

The compound (I′) can be produced by a method below.

wherein A¹, R¹ and R² have the same definition of the above.

The compound (I′) can be obtained by reacting a compound represented bythe formula (I′-1) with a compound represented by the formula (I′-2) inpresence of a basic catalyst in a solvent. Preferred examples of thebasic catalyst include pyridine. Preferred examples of the solventinclude tetrahydrofuran.

As the compound represented by the formula (I′-1), a marketed productmay be used. The hydroxyethyl methacrylate can be used as a marketedproduct.

The compound represented by the formula (I′-2) can be obtained byconverting corresponding carboxylic acid, depending on the kinds of R²,into an anhydride. The heptafluoro butyric anhydride can be used as amarketed product.

The resin (A1) may include a structural unit other than the structuralunit (I).

Examples of the structural unit other than the structural unit (I)include a structural unit derived from a monomer having an acid labilegroup described below (hereinafter may be referred to as “acid labilemonomer (a1)”), a structural unit derived from a monomer not having anacid labile group described below (hereinafter may be referred to as“acid stable monomer”), a structural unit derived from a known monomerin this field, a structural unit represented by the formula (IIIA)described below. Among these, a structural unit represented by theformula (IIIA) is preferable.

wherein R¹¹ represents a hydrogen atom or a methyl group;

ring W² represents a C₆ to C₁₀ hydrocarbon ring;

A¹² represents —O—, *—CO—O— or *—O—CO—, * represents a bond to ring W²;

R¹² represents a C₁ to C₆ hydrocarbon group having a fluorine atom.

The hydrocarbon ring of W² may be an alicyclic hydrocarbon ring, andpreferably a saturated alicyclic hydrocarbon ring.

Examples of the saturated alicyclic hydrocarbon ring include a ringbelow.

As the ring W², an adamantane ring and cyclohexane ring are preferable,and an adamantane ring is more preferable.

Examples of the R¹² include a group below.

Examples of the structural unit represented by the formula (IIIA)include structural units below.

Also, examples of the structural units (IIIA) include structural unitsin which a methyl group corresponding to R¹¹ in the structural unitsrepresented by the above is replaced by a hydrogen atom.

Among these, the structural unit (IIIA-1) and the structural unit(IIIA-1) in which a methyl group corresponding to R¹¹ in the structuralunits represented by the above is replaced by a hydrogen atom arepreferable.

The proportion of the structural unit (I) in the resin (A1) is generally5 to 100 mol %, preferably 10 to 100 mol %, more preferably 50 to 100mol %, still more preferably 80 to 100 mol %, and, in particular,preferably almost 100 mol %, with respect to the total structural units(100 mol %) constituting the resin (A1).

Within the proportion of the structural unit (I), it is possible toproduce a resist pattern with excellent line edge roughness and fewdefects.

When the resin (A1) contains the structural unit (IIIA), the proportionthereof in the resin (A1) is generally 1 to 95 mol %, preferably 2 to 80mol %, and more preferably 5 to 70 mol %, with respect to the totalstructural units (100 mol %) constituting the resin (A1).

For achieving the proportion of the structural unit (I) and/or thestructural unit (IIIA) in the resin (A1) within the above range, theamount of the compound (I′) and/or a monomer giving the structural unit(IIIA) to be used can be adjusted with respect to the total amount ofthe monomer to be used when the resin (A1) is produced (the same shallapply hereinafter for corresponding adjustment of the proportion).

The resin (A1) can be produced by a known polymerization method, forexample, radical polymerization method, using at least one of thecompound (I′) and/or at least one of the monomer giving the structuralunit (IIIA), and optionally at least one of the acid labile monomer(a1), least one of the acid stable monomer and/or at least one of aknown compound.

The weight average molecular weight of the resin (A) is preferably 5,000or more (more preferably 7,000 or more, and still more preferably 10,000or more), and 80,000 or less (more preferably 50,000 or less, and stillmore preferably 30,000 or less).

The weight average molecular weight is a value determined by gelpermeation chromatography using polystyrene as the standard product. Thedetailed condition of this analysis is described in Examples.

<Resin (A2)>

The resin (A2) is a resin having properties which is insoluble or poorlysoluble in alkali aqueous solution, but becomes soluble in an alkaliaqueous solution by the action of an acid. Here “becomes soluble in analkali aqueous solution by the action of an acid” means a resin that isinsoluble or poorly soluble in aqueous alkali solution before contactwith the acid, and becomes soluble in aqueous alkali solution aftercontact with an acid.

Therefore, the resin (A2) is preferably a resin having at least one ofthe structural unit derived from an acid labile monomer (a1) describedbelow.

Also, the resin (A2) may include a structural unit other than thestructural unit having the acid labile group as long as the resin (A2)has above properties.

Examples of the structural unit other than the structural unit havingthe acid labile group include a structural unit derived from the acidstable monomer, the structural unit derived from a known monomer in thisfield, the structural units represented by the formula (I) and theformula (IIIA) described above.

The resin (A2) may be a different resin from the resin (A1), or a resinwhich has the structural unit represented by the formula (I) and/or theformula (IIIA) described above so long as the resin (A2) has propertieswhich is insoluble or poorly soluble in alkali aqueous solution, butbecomes soluble in an alkali aqueous solution by the action of an acid.

<Acid Labile Monomer (a1)>

The “acid labile group” means a group which has an elimination group andin which the elimination group is detached by contacting with an acidresulting in forming a hydrophilic group such as a hydroxy or carboxygroup. Examples of the acid labile group include a group represented bythe formula (1) and a group represented by the formula (2). Hereinaftera group represented by the formula (1) may refer to as an “acid labilegroup (1)”, and a group represented by the formula (2) may refer to asan “acid labile group (2)”.

wherein R^(a1) to R^(a3) independently represent a C₁ to C₈ alkyl groupor a C₃ to C₂₀ alicyclic hydrocarbon group, or R^(a1) and R^(a2) may bebonded together to form a C₂ to C₂₀ divalent hydrocarbon group, *represents a bond. In particular, the bond here represents a bondingsite (the similar shall apply hereinafter for “bond”).

wherein R^(a1′) and R^(a2′) independently represent a hydrogen atom or aC₁ to C₁₂ hydrocarbon group, R^(a3′) represents a C₁ to C₂₀ hydrocarbongroup, or R^(a2′) and R^(a3′) may be bonded together to form a divalentC₂ to C₂₀ hydrocarbon group, and one or more —CH₂— contained in thehydrocarbon group or the divalent hydrocarbon group may be replaced by—O— or —S—, * represents a bond.

Examples of the alkyl group of R^(a1) to R^(a3) include methyl, ethyl,propyl, butyl, pentyl and hexyl groups.

Examples of the alicyclic hydrocarbon group of R^(a1) to R^(a3) includemonocyclic groups such as cyclopentyl, cyclohexyl, methylcyclohexyl,dimethylcyclohexyl, cycloheptyl, cyclooctyl groups; and polycyclichydrocarbon groups such as decahydronaphtyl, adamantyl, norbornyl (i.e.,bicyclo[2.2.1]hexyl), and methyl norbornyl groups as well as groupsbelow.

The alicyclic hydrocarbon group of R^(a1) and R^(a2) preferably has 3 to16 carbon atoms.

When R^(a1) and R^(a2) is bonded together to form a C₂ to C₂₀hydrocarbon group, examples of the group —C(R^(a1))(R^(a2))(R^(a3))include groups below. The divalent hydrocarbon group preferably has 3 to12 carbon atoms.

Specific examples of the acid labile group (1) include, for example,

1,1-dialkylalkoxycarbonyl group (a group in which R^(a1) to R^(a3) arealkyl groups, preferably tert-butoxycarbonyl group, in the formula (1)),

2-alkyladamantane-2-yloxycarbonyl group (a group in which R^(a1), R^(a2)and a carbon atom form adamantyl group, and R^(a3) is alkyl group, inthe formula (1)), and

1-(adamantine-1-yl)-1-alkylalkoxycarbonyl group (a group in which R^(a1)and R^(a2) are alkyl group, and R^(a3) is adamantyl group, in theformula (1)).

The hydrocarbon group of R^(a1′) to R^(a1′) includes any of an alkylgroup, an alicyclic hydrocarbon group and an aromatic hydrocarbon group.

Examples of the aromatic hydrocarbon group include an aryl group such asphenyl, naphthyl, anthryl, p-methylphenyl, p-tert-butylphenyl,p-adamantylphenyl, tolyl, xylyl, cumenyl, mesityl, biphenyl,phenanthryl, 2,6-diethylphenyl and 2-methyl-6-ethylphenyl groups.

Examples of the divalent hydrocarbon group which is formed by bondingwith R^(a2′) and R^(a3′) include groups in which a hydrogen atom in thehydrocarbon group of R² of the formula (I) is removed.

At least one of R^(a1′) and R^(a2′) is preferably a hydrogen atom.

Specific examples of the acid labile group (2) include a group below.

The acid labile monomer (a1) is preferably a monomer having an acidlabile group and a carbon-carbon double bond, and more preferably a(meth)acrylic monomer having the acid labile group.

Among the (meth)acrylic monomer having an acid labile group, it ispreferably a monomer having a C₅ to C₂₀ alicyclic hydrocarbon group.When a resin which can be obtained by polymerizing monomers having bulkystructure such as the alicyclic hydrocarbon group is used, the resistcomposition having excellent resolution tends to be obtained during theproduction of a resist pattern.

Examples of the (meth)acrylic monomer having the acid labile group and acarbon-carbon double bond preferably include a monomer represented bythe formula (a1-1) and a monomer represented by the formula (a1-2),below (hereinafter may be referred to as a “monomer (a1-1)” and a“monomer (a1-2)”). These may be used as a single monomer or as acombination of two or more monomers. The monomer (a1-1) induces astructural unit represented by the formula (a1-1), and the monomer(a1-2) induces a structural unit represented by the formula (a1-2) asdescribed below (hereinafter may be referred to as the “structural unit(a1-1)” and the “structural unit (a1-2)”).

wherein L^(a1) and L^(a2) independently represent *—O— or*—O—(CH₂)_(k1)—CO—O—, k1 represents an integer of 1 to 7, * represents abond to the carbonyl group;

R^(a4) and R^(a5) independently represent a hydrogen atom or a methylgroup;

R^(a6) and R^(a7) independently represent a C₁ to C₈ alkyl group or a C₃to C₁₀ alicyclic hydrocarbon group;

m1 represents an integer 0 to 14;

n1 represents an integer 0 to 10; and

n1′ represents an integer 0 to 3.

In the formula (a1-1) and the formula (a1-2), L^(a1) and L^(a2) arepreferably *—O— or *—O—(CH₂)_(k1′)—CO—O—, here k1′ represents an integerof 1 to 4 and more preferably 1, and more preferably *—O—.

R^(a4) and R^(a5) are preferably a methyl group.

Examples of the alkyl group of R^(a6) and R^(a7) include methyl, ethyl,propyl, butyl, pentyl, hexyl and octyl groups. Among these, the alkylgroup of R^(a6) and R^(a7) is preferably a C₁ to C₆ alkyl group,

Examples of the alicyclic group of R^(a6) and R^(a7) include monocyclichydrocarbon groups such as cyclopentyl, cyclohexyl, methylcyclohexyl,dimethylcyclohexyl, cycloheptyl, cyclooctyl groups; and polycyclichydrocarbon groups such as decahydronaphtyl, adamantyl, norbornyl (i.e.,bicyclo[2.2.1]hexyl), and methyl norbornyl groups as well as groupsbelow. Among these, the alicyclic group of R^(a6) and R^(a7) ispreferably a C₃ to C₈ alicyclic hydrocarbon group, and more preferably aC₃ to C₆ alicyclic hydrocarbon group.

m1 is preferably an integer of 0 to 3, and more preferably 0 or 1.

n1 is preferably an integer of 0 to 3, and more preferably 0 or 1.

n1′ is preferably 0 or 1, and more preferably 1.

Examples of the monomer (a1-1) include monomers described in JP2010-204646A. Among these, the monomers are preferably monomersrepresented by the formula (a1-1-1) to the formula (a1-1-8), and morepreferably monomers represented by the formula (a1-1-1) to the formula(a1-1-4) below.

Examples of the monomer (a1-2) include 1-ethylcyclopentane-1-yl(meth)acrylate, 1-ethylcyclohexane-1-yl (meth)acrylate,1-ethylcycloheptane-1-yl (meth)acrylate, 1-methylcyclopentane-1-yl(meth)acrylate and 1-isopropylcyclopentane-1-yl (meth)acrylate. Amongthese, the monomers are preferably monomers represented by the formula(a1-2-1) to the formula (a1-2-6), and more preferably monomersrepresented by the formula (a1-2-3) and the formula (a1-2-4), and stillmore preferably monomer represented by the formula (a1-2-3) below.

When the resin (A2) contains the structural unit derived from themonomer (a1-1) and/or the structural unit derived from the monomer(a1-2), the total proportion thereof is generally 10 to 95 mol %,preferably 15 to 90 mol %, more preferably 20 to 85 mol %, with respectto the total structural units (100 mol %) of the resin (A2).

Examples of a monomer having an acid-labile group (2) and acarbon-carbon double bond include a monomer represented by the formula(a1-5). Such monomer may be hereinafter referred to as “monomer (a1-5)”.When the resin (A2) has the structural unit derived from the monomer(a1-5), a resist pattern tends to be obtained with less defects.

wherein R³¹ represents a hydrogen atom, a halogen atom or a C₁ to C₆alkyl group that optionally has a halogen atom;

L¹, L² and L³ independently represent *—O—, *—S— or*—O—(CH₂)_(k1)—CO—O—, k1 represents an integer of 1 to 7, * represents abond to the carbonyl group (—CO—);

s1 represents an integer of 0 to 4;

s1′ represents an integer of 0 to 4;

Z¹ represents a single bond or a C₁ to C₆ alkanediyl group, and one ormore —CH₂— contained in the alkanediyl group may be replaced by —O— or—CO—.

In the formula (a1-5), R³¹ is preferably a hydrogen atom, a methyl groupor trifluoromethyl group;

L¹ is preferably —O—;

L² and L³ are independently preferably *—O— or *—S—, and more preferably—O— for one and —S— for another;

s1 is preferably 1;

s1′ is preferably an integer of 0 to 2;

Z¹ is preferably a single bond or —CH₂—CO—O—.

Examples of the compound represented by the formula (a1-5) includecompounds below.

When the resin (A2) contains the structural unit derived from themonomer represented by the formula (a1-5), the proportion thereof isgenerally 1 to 50 mol %, preferably 3 to 45 mol %, and more preferably 5to 40 mol %, with respect to the total structural units (100 mol %)constituting the resin (A2).

<Acid Stable Monomer>

As the acid stable monomer, a monomer having a hydroxy group or alactone ring is preferable. When a resin containing the structural unitderived from a monomer having hydroxy group (hereinafter such acidstable monomer may be referred to as “acid stable monomer (a2)”) or aacid stable monomer having a lactone ring (hereinafter such acid stablemonomer may be referred to as “acid stable monomer (a3)”) is used, theadhesiveness of resist to a substrate and resolution of resist tend tobe improved.

<Acid Stable Monomer (a2)>

The acid stable monomer (a2), which has the hydroxy group, is preferablyselected depending on the kinds of an exposure light source at producingthe resist pattern.

When KrF excimer laser lithography (248 nm), or high-energy irradiationsuch as electron beam or EUV light is used for the resist composition,using the acid stable monomer having a phenolic hydroxy group such ashydroxystyrene as the acid stable monomer (a2) is preferable.

When ArF excimer laser lithography (193 nm), i.e., short wavelengthexcimer laser lithography is used, using the acid stable monomer havinga hydroxy adamantyl group represented by the formula (a2-1) as the acidstable monomer (a2) is preferable.

The acid stable monomer (a2) having the hydroxy group may be used as asingle monomer or as a combination of two or more monomers.

Examples of the acid stable monomer having hydroxy adamantyl include themonomer represented by the formula (a2-1).

wherein L^(a3) represents —O— or *—O—(CH₂)_(k2)—CO—O—;

k2 represents an integer of 1 to 7;

* represents a bind to —CO—;

R^(a14) represents a hydrogen atom or a methyl group;

R^(a15) and R^(a16) independently represent a hydrogen atom, a methylgroup or a hydroxy group;

o1 represents an integer of 0 to 10.

In the formula (a2-1), L^(a3) is preferably —O—, —O—(CH₂)_(f1)—CO—O—,here f1 represents an integer of 1 to 4, and more preferably —O—.

R^(a14) is preferably a methyl group.

R^(a15) is preferably a hydrogen atom.

R^(a16) is preferably a hydrogen atom or a hydroxy group.

o1 is preferably an integer of 0 to 3, and more preferably an integer of0 or 1.

Examples of the acid stable monomer (a2-1) include monomers described inJP 2010-204646A. Among these, the monomers are preferably monomersrepresented by the formula (a2-1-1) to the formula (a2-1-6), morepreferably monomers represented by the formula (a2-1-1) to the formula(a2-1-4), and still more preferably monomers represented by the formula(a2-1-1) and the formula (a2-1-3) below.

When the resin (A2) contains the acid stable structural unit derivedfrom the monomer represented by the formula (a2-1), the proportionthereof is generally 3 to 40 mol %, preferably 5 to 35 mol %, morepreferably 5 to 30 mol %, and still more preferably 5 to 20 mol %, withrespect to the total structural units (100 mol %) constituting the resin(A2).

<Acid Stable Monomer (a3)>

The lactone ring included in the acid stable monomer (a3) may be amonocyclic compound such as β-propiolactone ring, γ-butyrolactone,δ-valerolactone, or a condensed ring with monocyclic lactone ring andother ring. Among these, γ-butyrolactone and condensed ring withγ-butyrolactone and other ring are preferable.

Examples of the acid stable monomer (a3) having the lactone ring includemonomers represented by the formula (a3-1), the formula (a3-2) and theformula (a3-3). These monomers may be used as a single monomer or as acombination of two or more monomers.

wherein L^(a4) to L^(a6) independently represent —O— or*—O—(CH₂)_(k3)—CO—O—;

k3 represents an integer of 1 to 7, * represents a bind to —CO—;

R^(a18) to R^(a20) independently represent a hydrogen atom or a methylgroup;

R^(a21) in each occurrence represents a C₁ to C₄ alkyl group;

p1 represents an integer of 0 to 5;

R^(a22) to R^(a23) in each occurrence independently represent a carboxylgroup, cyano group, and a C₁ to C₄ alkyl group;

q1 and r1 independently represent an integer of 0 to 3.

In the formulae (a3-1) to (a3-3), L^(a4) to L^(a6) include the samegroup as described in L^(a3) above, and are independently preferably—O—, *—O—(CH₂)_(k3′)—CO—O—, here k3′ represents an integer of 1 to 4(preferably 1), and more preferably —O—;

R^(a18) to R^(a21) are independently preferably a methyl group.

R^(a22) and R^(a23) are independently preferably a carboxyl group, cyanogroup or methyl group;

p1 to r1 are independently preferably an integer of 0 to 2, and morepreferably an integer of 0 or 1.

Examples of the monomer (a3) include monomers described in JP2010-204646A. Among these, the monomers are preferably monomersrepresented by the formula (a3-1-1) to the formula (a3-1-4), the formula(a3-2-1) to the formula (a3-2-4), the formula (a3-3-1) to the formula(a3-3-4), more preferably monomers represented by the formula (a3-1-1)to the formula (a3-1-2), the formula (a3-2-3) to the formula (a3-2-4),and still more preferably monomers represented by the formula (a3-1-1)and the formula (a3-2-3) below.

When the resin (A2) contains the structural units derived from the acidstable monomer (a3) having the lactone ring, the total proportionthereof is preferably 5 to 70 mol %, more preferably 10 to 65 mol %,still more preferably 15 to 60 mol %, with respect to the totalstructural units (100 mol %) constituting the resin (A2).

When the resin (A2) is the copolymer of the acid labile monomer (a1) andthe acid stable monomer, the proportion of the structural unit derivedfrom the acid labile monomer (a1) is preferably 10 to 80 mol %, and morepreferably 20 to 60 mol %, with respect to the total structural units(100 mol %) constituting the resin (A2).

The proportion of the structural unit derived from the monomer having anadamantyl group (in particular, the monomer having the acid labile group(a1-1)) is preferably 15 mol % or more with respect to the structuralunits derived from the acid labile monomer (a1). As the mole ratio ofthe structural unit derived from the monomer having an adamantyl groupincreases within this range, the dry etching resistance of the resultingresist improves.

The resin (A2) preferably is a copolymer of the acid labile monomer (a1)and the acid stable monomer. In this copolymer, the acid labile monomer(a1) is preferably at least one of the acid labile monomer (a1-1) havingan adamantyl group and the acid labile monomer (a1-2) having acyclohexyl group, and more preferably is the acid labile monomer (a1-1).

The acid stable monomer is preferably the acid stable monomer (a2)having a hydroxy group and/or the acid stable monomer (a3) having alactone ring. The acid stable monomer (a2) is preferably the monomerhaving the hydroxyadamantyl group (a2-1).

The acid stable monomer (a3) is preferably at least one of the monomerhaving the γ-butyrolactone ring (a3-1) and the monomer having thecondensed ring of the γ-butyrolactone ring and the norbornene ring(a3-2).

The resin (A2) can be produced by a known polymerization method, forexample, radical polymerization method, using at least one of the acidlabile monomer (a1) and/or at least one of the acid stable monomer (a2)having a hydroxy group and/or at least one of the acid stable monomer(a3) having a lactone ring and/or at least one of a known compound.

The weight average molecular weight of the resin (A2) is preferably2,500 or more (more preferably 3,000 or more, and still more preferably4,000 or more), and 50,000 or less (more preferably 30,000 or less, andstill more preferably 15,000 or less).

In the present resist composition, the weight ratio of the resins(A1)/(A2) (weight ratio) is preferably, for example, 0.01/10 to 5/10,more preferably 0.05/10 to 3/10, still more preferably 0.1/10 to 2/10,in particular, preferably 0.2/10 to 1/10.

<Resin Other than Resin (A1) and Resin (A2)>

The resist composition of the present invention may include a resinother than the resin (A1) and the resin (A2) described above. Such resinis a resin having a structural unit derived from the acid labilemonomer, the acid stable monomer, as described above, and/or a knownmonomer in this field.

When the resist composition of the present invention include a resinother than the resin (A1) and the resin (A2), the proportion thereof isgenerally 0.1 to 50 weight %, preferably 0.5 to 30 weight %, and morepreferably 1 to 20 weight %, with respect to the total structural units(100 weight %) of the resin (A) in the resist composition.

The proportion of the resin (A) can be adjusted with respect to thetotal solid proportion of the resist composition. For example, theresist composition of the present invention preferably contains 80weight % or more and 99 weight % or less of the resin (A), with respectto the total solid proportion of the resist composition.

In the specification, the term “solid proportion of the resistcomposition” means the entire proportion of all ingredients other thanthe solvent (E). For example, if the proportion of the solvent (E) is 90weight %, the solid proportion of the resist composition is 10 weight %.

The proportion of the resin (A) and the solid proportion of the resistcomposition can be measured with a known analytical method such as, forexample, liquid chromatography and gas chromatography.

<Acid Generator (B)>

The acid generator (B) is classified into non-ionic-based or ionic-basedacid generator. The present resist composition may be used either acidgenerators.

Examples of the non-ionic-based acid generator include organichalogenated compounds; sulfonate esters such as 2-nitrobenzyl ester,aromatic sulfonate, oxime sulfonate, N-sulfonyl oxyimide, sulfonyloxyketone and diazo naphthoquinone 4-sulfonate; sulfones such asdisulfone, ketosulfone and sulfone diazomethane.

Examples of the ionic acid generator includes onium salts containingonium cation (such as diazonium salts, phosphonium salts, sulfoniumsalts, iodonium salts).

Examples of anion of onium salts include sulfonate anion, sulfonylimideanion and sulfonylmethyde anion.

For the acid generator (B), compounds which generate an acid byradiation described in JP S63-26653-A, JP S55-164824-A, JP S62-69263-A,JP S63-146038-A, JP S63-163452-A, JP S62-153853-A, JP S63-146029-A, U.S.Pat. No. 3,779,778-B, U.S. Pat. No. 3,849,137-B, DE3,914,407-B andEP-126,712-A can be used.

Also, as the acid generator (B), compounds formed according toconventional methods can be used

The acid generator (B) is preferably a fluorine-containing acidgenerator represented by the formula (B1) as described below. In theacid generator (B1), electropositive Z⁺ hereinafter may be referred toas “an organic cation”, and electronegative one in which the organiccation has been removed from the compound may be referred to as“sulfonate anion”.

wherein Q¹ and Q² independently represent a fluorine atom or a C₁ to C₆perfluoroalkyl group;

L^(b1) represents a single bond or an C₁ to C₁₇ divalent saturatedhydrocarbon group, and one or more —CH₂— contained in the divalentsaturated hydrocarbon group may be replaced by —O— or —CO—;

Y represents an optionally substituted C₁ to C₁₈ alkyl group or anoptionally substituted C₃ to C₁₈ alicyclic hydrocarbon group, and one ormore —CH₂— contained in the alkyl group and alicyclic hydrocarbon groupmay be replaced by —O—, —CO— or —SO₂—; and

Z⁺ represents an organic cation.

Examples of the perfluoroalkyl group of Q¹ and Q² includetrifluoromethyl, perfluoroethyl, perfluoropropyl, perfluoro-isopropyl,perfluorobutyl, perfluoro-sec-butyl, perfluoro-tert-butyl,perfluoropentyl and perfluorohexyl groups.

Among these, Q¹ and Q² independently are preferably trifluoromethyl orfluorine atom, and more preferably a fluorine atom.

Examples of the a divalent saturated hydrocarbon group of L^(b1) includeany of;

a chain alkanediyl group such as methylene, ethylene, propane-1,3-diyl,propane-1,2-diyl, butane-1,4-diyl, pentane-1,5-diyl, hexane-1,6-diyl,heptane-1,7-diyl, octane-1,8-diyl, nonane-1,9-diyl, decane-1,10-diyl,undecane-1,11-diyl, dodecane-1,12-diyl, tridecane-1,13-diyl,tetradecane-1,14-diyl, pentadecane-1,15-diyl, hexadecane-1,16-diyl,heptadecane-1,17-diyl groups, methane-1,1-diyl, ethane-1,1-diyl,propan-1,1-diyl and propan-2,2-diyl groups;

a branched chain alkanediyl group such as a group in which a chainalkanediyl group is bonded a side chain of a C₁ to C₄ alkyl group suchas methyl, ethyl, propyl, isopropyl, butyl, sec-butyl and tert-butyl,for example, butan-1,3-diyl, 2-methylpropane-1,3-diyl,2-methylpropane-1,2-diyl, pentane-1,4-diyl, 2-methylbutane-1,4-diylgroups;

a mono-alicyclic hydrocarbon group such as cycloalkanediyl, for example,cyclobutan-1,3-diyl, cyclopentan-1,3-diyl, cyclohexane-1,4-diyl,cyclooctan-1,5-diyl groups;

a poly-alicyclic hydrocarbon group such as norbornane-1,4-diyl,norbornane-2,5-diyl, adamantane-1,5-diyl and adamantane-2,6-diyl groups;and

a combination of two or more groups.

Examples of the saturated hydrocarbon group of L^(b1) in which one ormore —CH₂— contained in the saturated hydrocarbon group is replaced by—O— or —CO— include groups represented by the formula (b1-1) to theformula (b1-6) below. In the formula (b1-1) to the formula (b1-6), thegroup is represented so as to correspond with two sides of the formula(B1), that is, the left side of the group bonds to C(Q¹)(Q²)— and theright side of the group bonds to —Y (examples of the formula (b1-1) tothe formula (b1-6) are the same as above). * represents a bond.

wherein L^(b2) represents a single bond or a C₁ to C₁₅ divalentsaturated hydrocarbon group;

L^(b3) represents a single bond or a C₁ to C₁₂ divalent saturatedhydrocarbon group;

L^(b4) represents a C₁ to C₁₃ divalent saturated hydrocarbon group, thetotal number of the carbon atoms in L^(b3) and L^(b4) is at most 13;

L^(b5) represents a C₁ to C₁₅ divalent saturated hydrocarbon group;

L^(b6) and L^(b7) independently represent a C₁ to C₁₅ divalent saturatedhydrocarbon group, the total number of the carbon atoms in L^(b6) andL^(b7) is at most 16;

L^(b8) represents a C₁ to C₁₄ divalent saturated hydrocarbon group;

L^(b9) and L^(b10) independently represent a C₁ to C₁₁ divalentsaturated hydrocarbon group, the total number of the carbon atoms inL^(b9) and L^(b10) is at most 12.

Among these, L^(b1) is preferably the groups represented by the formula(b1-1) to the formula (b1-4), more preferably the group represented bythe formula (b1-1) or the formula (b1-2), and still more preferably thegroup represented by the formula (b1-1). In particular, the divalentgroup represented by the formula (b1-1) in which L^(b2) represents asingle bond or —CH₂— is preferable.

Specific examples of the divalent group represented by the formula(b1-1) include groups below. In the formula below, * represent a bond.

Specific examples of the divalent group represented by the formula(b1-2) include groups below.

Specific examples of the divalent group represented by the formula(b1-3) include groups below.

Specific examples of the divalent group represented by the formula(b1-4) include a group below.

Specific examples of the divalent group represented by the formula(b1-5) include groups below.

Specific examples of the divalent group represented by the formula(b1-6) include groups below.

The alkyl group of Y is preferably a C₁ to C₆ alkyl group.

Examples of the alicyclic hydrocarbon group of Y include groupsrepresented by the formula (Y1) to the formula (Y11).

Y may have a substituent.

Examples of the substituent of Y include a halogen atom, a hydroxygroup, an oxo group, a C₁ to C₁₂ alkyl group, a hydroxy group-containingC₁ to C₁₂ alkyl group, a C₃ to C₁₆ alicyclic hydrocarbon group, a C₁ toC₁₂ alkoxy group, a C₆ to C₁₈ aromatic hydrocarbon group, a C₇ to C₂₁aralkyl group, a C₂ to C₄ acyl group, a glycidyloxy group or a—(CH₂)_(j2)—O—CO—R^(b1) group, wherein R^(b1) represents a C₁ to C₁₆alkyl group, a C₃ to C₁₆ alicyclic hydrocarbon group or a C₆ to C₁₈aromatic hydrocarbon group, j2 represents an integer of 0 to 4. Thealkyl group, alicyclic hydrocarbon group, aromatic hydrocarbon group andthe aralkyl group of the substituent may further have a substituent suchas a C₁ to C₆ alkyl group, a halogen atom, a hydroxy group and an oxogroup.

Examples of the hydroxy group-containing alkyl group includehydroxymethyl and hydroxyethyl groups

Examples of the aralkyl group include benzyl, phenethyl, phenylpropyl,naphthylmethyl and naphthylethyl groups.

Examples of alicyclic hydrocarbon group of Y in which one or more —CH₂—contained in the alicyclic hydrocarbon group is replaced by —O—, —CO— or—SO₂— include groups represented by the formula (Y12) to the formula(Y26).

Among these, the alicyclic hydrocarbon group is preferably any one ofgroups represented by the formula (Y1) to the formula (Y19), morepreferably any one of groups represented by the formula (Y11), (Y14),(Y15) or (Y19), and still more preferably group represented by theformula (Y11) or (Y14).

Examples of Y include the groups below.

When Y represents an alkyl group and L^(b1) represents a C₁ to C₁₇divalent alicyclic hydrocarbon group, the —CH₂— contained in thedivalent alicyclic hydrocarbon group bonding Y is preferably replaced byan oxygen atom or carbonyl group. In this case, the —CH₂— contained inthe alkyl group constituting Y is not replaced by an oxygen atom orcarbonyl group.

Y is preferably an optionally substituted C₃ to C₁₈ alicyclichydrocarbon group, more preferably an adamantyl group which isoptionally substituted, for example, an oxo group and a hydroxy group,and still more preferably an adamantyl group, a hydroxyadamantyl groupand an oxoadamantyl group.

The sulfonate anion is preferably a sulfonate anions represented by theformula (b1-1-1) to the formula (b1-1-9) below. In the formula (b1-1-1)to the formula (b1-1-9), Q¹, Q² and L^(b2) represents the same meaningas defined above. R^(b2) and R^(b3) independently represent a C₁ to C₄alkyl group (preferably methyl group).

Specific examples of the sulfonate anion include sulfonate anionsdescribed in JP2010-204646A.

Examples of the cation of the acid generator (B) include an organiconium cation, for example, organic sulfonium cation, organic iodoniumcation, organic ammonium cation, benzothiazolium cation and organicphosphonium cation. Among these, organic sulfonium cation and organiciodonium cation are preferable, and aryl sulfonium cation is morepreferable.

Z⁺ of the formula (B1) is preferably represented by any of the formula(b2-1) to the formula (b2-4).

wherein R^(b4), R^(b5) and R^(b6) independently represent a C₁ to C₃₀hydrocarbon group, the hydrocarbon group is preferably a C₁ to C₃₀ alkylgroup, a C₃ to C₁₈ alicyclic hydrocarbon group or a C₆ to C₁₈ aromatichydrocarbon group, the alkyl group may be substituted with a hydroxygroup, a C₁ to C₁₂ alkoxy group or a C₆ to C₁₈ aromatic hydrocarbongroup, the alicyclic hydrocarbon group may be substituted with a halogenatom, a C₂ to C₄ acyl group and a glycidyloxy group, the aromatichydrocarbon group may be substituted with a halogen atom, a hydroxygroup, a C₁ to C₁₈ alkyl group, a C₃ to C₁₈ alicyclic hydrocarbon groupor a C₁ to C₁₂ alkoxy group;

R^(b7) and R^(b8) in each occurrence independently represent a hydroxygroup, a C₁ to C₁₂ alkyl group or a C₁ to C₁₂ alkoxyl group;

m2 and n2 independently represent an integer of 0 to 5;

R^(b9) and R^(b10) independently represent a C₁ to C₁₈ alkyl group or aC₃ to C₁₈ alicyclic hydrocarbon group, or R^(b9) and R^(b10) may bebonded together with a sulfur atom bonded thereto to form asulfur-containing 3- to 12-membered (preferably 3- to 7-membered) ring,and one or more —CH₂— contained in the ring may be replaced by —O—, —S—or —CO—;

R^(b11) represents a hydrogen atom, a C₁ to C₁₈ alkyl group, a C₃ to C₁₈alicyclic hydrocarbon group or a C₆ to C₁₈ aromatic hydrocarbon group;

R^(b12) represents a C₁ to C₁₂ alkyl group, a C₃ to C₁₈ alicyclichydrocarbon group and a C₆ to C₁₈ aromatic hydrocarbon group, thearomatic hydrocarbon group may be substituted with a C₁ to C₁₂ alkylgroup, a C₁ to C₁₂ alkoxy group, a C₃ to C₁₈ alicyclic hydrocarbon groupor a C₁ to C₁₂ alkyl carbonyloxy group;

R^(b11) and R^(b12) may be bonded together with —CH—CO— bonded theretoto form a 3- to 12-membered (preferably a 3- to 7-membered) ring, andone or more —CH₂— contained in the ring may be replaced by —O—, —S— or—CO—;

R^(b13), R^(b14), R^(b15), R^(b16), R^(b17) and R^(b18) is in eachoccurrence independently represent a hydroxy group, a C₁ to C₁₂ alkylgroup or a C₁ to C₁₂ alkoxy group;

L^(b11) represents —S— or —O—;

o2, p2, s2 and t2 independently represent an integer of 0 to 5;

q2 or r2 independently represent an integer of 0 to 4;

u2 represents an integer of 0 or 1.

Examples of the alkyl group include methyl, ethyl, n-propyl, isopropyl,n-butyl, sec-butyl, tert-butyl, pentyl, hexyl, octyl and 2-ethylhexylgroups. In particular, the alkyl group of R^(b9) to R^(b11) ispreferably a C₁ to C₁₂ alkyl group.

Examples of the alicyclic hydrocarbon group include a monocyclichydrocarbon groups such as cyclopropyl, cyclobutyl, cyclopentyl,cyclohexyl, cycloheptyl, cyclodecyl, 2-alkyladamantane-2-yl,1-(adamatane-1-yl)-1-alkyl and isobornyl groups. In particular, thealicyclic hydrocarbon group of R^(b9) to R^(b11) is preferably a C₃ toC₁₈ alicyclic hydrocarbon group and more preferably a C₄ to C₁₂alicyclic hydrocarbon group.

Examples of the aromatic hydrocarbon group include phenyl, naphthyl,4-methylphenyl, 4-ethylphenyl, 4-t-butylphenyl, 4-cyclohexylphenyl,4-methoxyphenyl and biphenyl groups.

Examples of the aromatic group substituted with an alkyl group typicallyrepresent an aralkyl group such as benzyl and phenethyl groups.

Examples of the alkoxy group include methoxy, ethoxy, propoxy, butoxy,pentyloxy, hexyloxy, heptyloxy, octyloxy, decyloxy and dodecyloxygroups.

Examples of the halogen atom include chlorine, bromine and iodine atoms.

Examples of the acyl group include acetyl, propionyl and butyryl groups.

Examples of the alkyl carbonyloxy group of the R^(b12) include methylcarbonyloxy, ethyl carbonyloxy, n-propyl carbonyloxy, isopropylcarbonyloxy, n-butyl carbonyloxy, sec-butyl carbonyloxy, tert-butylcarbonyloxy, pentyl carbonyloxy, hexyl carbonyloxy, octylcarbonyloxy and2-ethylhexylcarobonyloxy groups.

Examples of the ring having —CH—CO— and formed by R^(b9) and R^(b10)bonded together include thiolane-1-ium ring (tetrahydrothiopheniumring), thian-1-ium ring and 1,4-oxathian-4-ium ring.

Examples of the ring having a sulfur atom and formed by R^(b11) andR^(b12) bonded together include oxocycloheptane ring, oxocyclohexanering, oxonorbornane ring and oxoadamantane ring.

Among the cations represented by the formula (b2-1) to the formula(b2-4), the cation represented by the formula (b2-1-1) is preferable,and triphenyl sulfonium cation (v2=w2=x2=0 in the formula (b2-1-1)),diphenyltolyl sulfonium cation (v2=w2=0, x2=1, and R^(b21) is a methylgroup in the formula (b2-1-1)) and tritolyl sulfonium cation(v2=w2=x2=1, R^(b19), R^(b20) and R^(b21) are a methyl group in theformula (b2-1-1)) are more preferable.

wherein R^(b19), R^(b20) and R^(b21) in each occurrence independentlyrepresent a halogen atom, a hydroxy group, a C₁ to C₁₂ alkyl group, a C₃to C₁₈ alicyclic hydrocarbon group or a C₁ to C₁₂ alkoxy group, and thealkyl group, the alicyclic hydrocarbon group and the alkoxy group may besubstituted with a halogen group, a hydroxy group, a C₁ to C₁₂ alkoxygroup, a C₆ to C₁₈ aromatic hydrocarbon group, a C₂ to C₄ acyl group ora glycidyloxy group;

v2 to x2 independently represent an integer of 0 to 5.

In the formula (b2-1-1), R^(b19) to R^(b21) independently preferablyrepresent a halogen atom (and more preferably fluorine atom), a hydroxygroup, a C₁ to C₁₂ alkyl group or a C₁ to C₁₂ alkoxy group; and

v2 to x2 independently represent preferably 0 or 1.

Specific examples of the organic cations represented by the formula(b2-1) to the formula (b2-4) include, for example, compounds describedin JP2010-204646A.

The acid generator (B1) is a compound in combination of the abovesulfonate anion and an organic cation.

The above sulfonate anion and the organic cation may optionally becombined, combinations which are any of anions represented by theformula (b1-1-1) to the formula (b1-1-9) and any of cations (b2-1-1),and combinations which are any of anions represented by the formula(b1-1-3) to the formula (b1-1-5) and any of cations (b2-3) arepreferable.

Preferred acid generators (B1) are represented by the formula (B1-1) tothe formula (B1-17). Among these, the formulae (B1-1), (B1-2), (B1-6),(B1-11), (B1-12), (B1-13) and (B1-14) which contain triphenyl sulfoniumcation, and the formulae (B1-3) and (B1-7) which contain tritolylsulfonium cation are preferable.

The proportion of the acid generator (B) is preferably not less than 1parts by weight (and more preferably not less than 3 parts by weight),and not more than 30 parts by weight (and more preferably not more than25 parts by weight), with respect to 100 parts by weight of the resin(A2).

In the resist composition of the present invention, the acid generatormay be used as a single salt or as a combination of two or more salts.

<Compound (II)>

The compound (II) is the compound represented by the formula (II) below.

wherein R³ and R⁴ in each occurrence independently represent a C₁ to C₁₂hydrocarbon group, a C₁ to C₆ alkoxyl group, a C₂ to C₇ acyl group, a C₂to C₇ acyloxy group, a C₂ to C₇ alkoxycarbonyl group, a nitro group or ahalogen atom;

m′ and n′ independently represent an integer of 0 to 4.

In the formula (II), R³ and R⁴ independently preferably represent a C₁to C₆ hydrocarbon group, a C₁ to C₄ alkoxyl group, a C₂ to C₅ acylgroup, a C₂ to C₅ acyloxy group, a C₂ to C₅ alkoxycarbonyl group, anitro group or a halogen atom

m′ and n′ independently preferably represent an integer of 0 to 3, andmore preferably an integer of 0 to 2.

The hydrocarbon group may be any of an aliphatic hydrocarbon group, anaromatic hydrocarbon group and a combination of two or more such groups.The aliphatic hydrocarbon group may be any of a chain and cyclicaliphatic hydrocarbon group, and a combination of two or more suchgroups. The aliphatic hydrocarbon group is preferably an alkyl group andan alicyclic group.

Examples of the alkyl group include methyl, ethyl, n-propyl, iso-propyl,n-butyl, sec-butyl, tert-butyl, iso-butyl, n-pentyl, iso-pentyl,tert-pentyl, neo-pentyl, hexyl and nonyl groups.

The alicyclic hydrocarbon group may be either monocyclic or polycyclichydrocarbon group, and saturated or unsaturated hydrocarbon group.Examples of the alicyclic hydrocarbon group include cycloalkyl groupssuch as cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl,cyclodecyl; adamantyl and norbornyl groups. Among these, saturatedalicyclic hydrocarbon groups are preferable.

Examples of the aromatic hydrocarbon group include an aryl group such asphenyl, 1-naphthyl, 2-naphthyl, 2-methylphenyl, 3-methylphenyl,4-methylphenyl, 4-ethylphenyl, 4-propylphenyl, 4-isopropylphenyl,4-bytylphenyl, 4-tert-bytylphenyl, 4-hexylphenyl, 4-cyclohexylphenyl,anthryl, p-adamantylphenyl, tolyl, xylyl, cumenyl, mesityl, biphenyl,phenanthryl, 2,6-diethylphenyl and 2-methyl-6-ethylphenyl groups.

Examples of the combination thereof include an alkyl-cycloalkyl group, acycloalkyl-alkyl group, an aralkyl group such as phenylmethyl,1-phenylethyl, 2-phenylethyl, 1-phenyl-1-propyl, 1-phenyl-2-propyl,2-phenyl-2-propyl, 3-phenyl-1-propyl, 4-phenyl-1-butyl,5-phenyl-1-phenyl and 6-phenyl-1-hexyl groups.

Examples of the alkoxy group include methoxy, ethoxy, propoxy, butoxy,pentyloxy, hexyloxy, heptyloxy, octyloxy, decyloxy and dodecyloxygroups.

Examples of the acyl group include acetyl, propionyl, benzoyl andcyclohexane carbonyl groups.

Examples of the acyloxy group include groups in which an oxy group isbonded to the above acyl group.

Examples of the alkoxycarbonyl group include groups in which a carbonylgroup is bonded to the above alkoxyl group, such as methoxycarbonyl,ethoxycarbonyl, n-propoxycarbonyl, isopropoxycarbonyl, n-butoxycarbonyl,sec-butoxycarbonyl, and tert-butoxycarbonyl groups.

Examples of the halogen atom include chlorine, bromine and iodine atoms.

Specific examples of the compound (II) include compounds below.

In the resist composition of the present invention, the proportion ofthe compound (II) is preferably 0.01 to 5 weight %, and more preferably0.01 to 3 weight %, and still more preferably 0.01 to 1 weight % withrespect to total solid proportion of the resist composition.

The compound (II) may be used as a single compound or as a combinationof two or more compounds.

<Solvent (E)″>

The resist composition of the present invention may include a solvent(E) in the amount of 90 weight % or more, preferably 92 weight % ormore, and more preferably 94 weight % or more, and 99.9 weight % orless, preferably 99 weight % or less in the composition.

The content of the solvent (E) can be measured with a known analyticalmethod such as, for example, liquid chromatography and gaschromatography.

Examples of the solvent (E) include glycol ether esters such asethylcellosolve acetate, methylcellosolve acetate and propylene glycolmonomethyl ether acetate; glycol ethers such as propylene glycolmonomethyl ether; ethers such as diethylene glycol dimethyl ether;esters such as ethyl lactate, butyl acetate, amyl acetate and ethylpyruvate; ketones such as acetone, methyl isobutyl ketone, 2-heptanoneand cyclohexanone; and cyclic esters such as γ-butyrolactone. Thesesolvents may be used as a single solvent or as a mixture of two or moresolvents.

<Basic Compound (C)>

The resist composition of the present invention may contain a basiccompound (C). The basic compound (C) is a compound having a property toquench an acid, in particular, generated from the acid generator (B),and called “quencher”.

As the basic compounds (C), nitrogen-containing basic compounds (forexample, amine and basic ammonium salt) are preferable. The amine may bean aliphatic amine or an aromatic amine. The aliphatic amine includesany of a primary amine, secondary amine and tertiary amine. The aromaticamine includes an amine in which an amino group is bonded to an aromaticring such as aniline, and a hetero-aromatic amine such as pyridine.

Preferred basic compounds (C) include compounds presented by the formula(C1) to the formula (C8) as described below. Among these, the basiccompound presented by the formula (C1-1) is more preferable.

wherein R^(c1), R^(c2) and R^(c3) independently represent a hydrogenatom, a C₁ to C₆ alkyl group, C₅ to C₁₀ alicyclic hydrocarbon group or aC₆ to C₁₀ aromatic hydrocarbon group, one or more hydrogen atomcontained in the alkyl group and alicyclic hydrocarbon group may bereplaced by a hydroxy group, an amino group or a C₁ to C₆ alkoxyl group,one or more hydrogen atom contained in the aromatic hydrocarbon groupmay be replaced by a C₁ to C₆ alkyl group, a C₁ to C₆ alkoxyl group, aC₅ to C₁₀ alicyclic hydrocarbon group or a C₆ to C₁₀ aromatichydrocarbon group.

wherein R^(c2) and R^(c3) have the same definition of the above;

R^(c4) in each occurrence represents a C₁ to C₆ alkyl group, a C₁ to C₆alkoxyl group, a C₅ to C₁₀ alicyclic hydrocarbon group or a C₆ to C₁₀aromatic hydrocarbon group;

m3 represents an integer 0 to 3.

wherein R^(c5), R^(c6), R^(c7) and R^(c8) independently represent theany of the group as described in R^(c1) of the above;

R^(c9) in each occurrence independently represents a C₁ to C₆ alkylgroup, a C₃ to C₆ alicyclic hydrocarbon group or a C₂ to C₆ alkanoylgroup;

n3 represents an integer of 0 to 8.

Examples of the alkanoyl group include acetyl group, 2-methylacetylgroup, 2,2-dimethylacetyl group, propionyl group, butylyl group,isobutylyl group, pentanoyl group, and 2,2-dimethylpropionyl group.

wherein R^(c10), R^(c11), R^(c12), R^(c13) and R^(c16) independentlyrepresent the any of the groups as described in R^(c1);

R^(c14), R^(c15) and R^(c17) in each occurrence independently representthe any of the groups as described in R^(c4);

o3 and p3 represent an integer of 0 to 3;

L^(c1) represents a divalent C₁ to C₆ alkanediyl group, —CO—, —C(═NH)—,—S— or a combination thereof.

wherein R^(c18), R^(c19) and R^(c20) in each occurrence independentlyrepresent the any of the groups as described in R^(c4);

q3, r3 and s3 represent an integer of 0 to 3;

L^(c2) represents a single bond, a C₁ to C₆ alkanediyl group, —CO—,—C(═NH)—, —S— or a combination thereof.

Specific examples of the amine represented by the formula (C1) include1-naphtylamine and 2-naphtylamine, aniline, diisopropylaniline, 2-, 3-or 4-methylaniline, 4-nitroaniline, N-methylaniline,N,N-dimethylaniline, diphenylamine, hexylamine, heptylamine, octylamine,nonylamine, decylamine, dibutylamine, dipentylamine, dihexylamine,diheptylamine, dioctylamine, dinonylamine, didecylamine, triethylamine,trimethylamine, tripropylamine, tributylamine, tripentylamine,trihexylamine, triheptylamine, trioctylamine, trinonylamine,tridecylamine, methyldibutylamine, methyl dipentylamine,methyldihexylamine, methyldicyclohexylamine, methyldiheptylamine,methyldioctylamine, methyldinonylamine, methyldidecylamine,ethyldibutylamine, ethyldipentylamine, ethyldihexylamine,ethyldiheptylamine, ethyldioctylamine, ethyldinonylamine,ethyldidecylamine, dicyclohexylmethylamine,tris[2-(2-methoxyethoxy)ethyl]amine, triisopropanolamine, ethylenediamine, tetramethylene diamine, hexamethylene diamine,4,4′-diamino-1,2-diphenylethane,4,4′-diamino-3,3′-dimethyldiphenylmethane and4,4′-diamino-3,3′-diethyldiphenylmethane.

Among these, diisopropylaniline is preferable, particularly2,6-diisopropylaniline is more preferable as the basic compounds (C)contained in the present resist composition.

Specific examples of the compound represented by the formula (C2)include, for example, piperadine.

Specific examples of the compound represented by the formula (C3)include, for example, morpholine.

Specific examples of the compound represented by the formula (C4)include, for example, piperidine, a hindered amine compound havingpiperidine skeleton described in JP H11-52575-A.

Specific examples of the compound represented by the formula (C5)include, for example, 2,2′-methylenebisaniline.

Specific examples of the compound represented by the formula (C6)include, for example, imidazole and 4-methylimidazole.

Specific examples of the compound represented by the formula (C7)include, for example, pyridine and 4-methylpyrizine.

Specific examples of the compound represented by the formula (C8)include, for example, 1,2-di(2-pyridyl)ethane, 1,2-di(4-pyridyl)ethane,1,2-di(2-pyridyl)ethene, 1,2-di(4-pyridyl)ethene,1,3-di(4-pyridyl)propane, 1,2-di(4-pyridyloxy)ethane,di(2-pyridyl)ketone, 4,4′-dipyridyl sulfide, 4,4′-dipyridyl disulfide,2,2′-dipyridylamine, 2,2′-dipicolylamine and bipyridine.

Examples of the ammonium salt include tetramethylammonium hydroxide,tetraisopropylammonium hydroxide, tetrabutylammonium hydroxide,tetrahexylammonium hydroxide, tetraoctylammonium hydroxide,phenyltrimethyl ammonium hydroxide,3-(trifluoromethyl)phenyltrimethylammonium hydroxide, tetra-n-butylammonium salicylate and choline.

The proportion of the basic compound (C) is preferably 0.01 to 5 weight%, more preferably 0.01 to 3 weight %, and still more preferably 0.01 to1 weight % with respect to the total solid proportion of the resistcomposition.

<Other Ingredient (Hereinafter may be Referred to as “Other Ingredient(F)”>

The resist composition can also include small amounts of variousadditives such as sensitizers, dissolution inhibitors, surfactants,stabilizers, and dyes, as needed.

<Preparing the Resist Composition>

The present resist composition can be prepared by mixing the resin (A1),the resin (A2), the acid generator and the compound (II), and the basiccompound (C), the solvent (E) and the other ingredient (F) as needed.There is no particular limitation on the order of mixing. The mixing maybe performed in an arbitrary order. The temperature of mixing may beadjusted to an appropriate temperature within the range of 10 to 40° C.,depending on the kinds of the resin and solubility in the solvent (E) ofthe resin. The time of mixing may be adjusted to an appropriate timewithin the range of 0.5 to 24 hours, depending on the mixingtemperature. There is no particular limitation to the tool for mixing.An agitation mixing may be adopted.

After mixing the above ingredients, the present resist compositions canbe prepared by filtering the mixture through a filter having about 0.003to 0.2 μm pore diameter.

<Method for Producing Resist Pattern>

The method for producing resist pattern of the present inventionincludes the steps of:

(1) applying the resist composition of the present invention onto asubstrate;

(2) drying the applied composition to form a composition layer;

(3) exposing the composition layer;

(4) heating the exposed composition layer, and

(5) developing the heated composition layer.

Applying the resist composition onto the substrate can generally becarried out through the use of a resist application device, such as aspin coater known in the field of semiconductor microfabricationtechnique. The thickness of the applied resist composition layer can beadjusted by controlling the variable conditions of the resistapplication device. These conditions can be selected based on apre-experiment carried out beforehand. The substrate can be selectedfrom various substrates intended to be microfabricated. The substratemay be washed, and an organic antireflection film may be formed on thesubstrate by use of a commercially available antireflection composition,before the application of the resist composition.

Drying the applied composition layer, for example, can be carried outusing a heating device such as a hotplate (so-called “prebake”), adecompression device, or a combination thereof. Thus, the solventevaporates from the resist composition and a composition layer with thesolvent removed is formed. The condition of the heating device or thedecompression device can be adjusted depending on the kinds of thesolvent used. The temperature in this case is generally within the rangeof 50 to 200° C. Moreover, the pressure is generally within the range of1 to 1.0×10⁵ Pa.

The composition layer thus obtained is generally exposed using anexposure apparatus or a liquid immersion exposure apparatus. Theexposure is generally carried out through a mask that corresponds to thedesired pattern. Various types of exposure light source can be used,such as irradiation with ultraviolet lasers such as KrF excimer laser(wavelength: 248 nm), ArF excimer laser (wavelength: 193 nm), F₂ excimerlaser (wavelength: 157 nm), or irradiation with far-ultravioletwavelength-converted laser light from a solid-state laser source (YAG orsemiconductor laser or the like), or vacuum ultraviolet harmonic laserlight or the like. Also, the exposure device may be one which irradiateselectron beam or extreme-ultraviolet light (EUV).

After exposure, the composition layer is subjected to a heat treatment(so-called “post-exposure bake”) to promote the deprotection reaction.The heat treatment can be carried out using a heating device such as ahotplate. The heating temperature is generally in the range of 50 to200° C., preferably in the range of 70 to 150° C.

The composition layer is developed after the heat treatment, generallywith an alkaline developing solution and using a developing apparatus.The development here means to bring the composition layer after the heattreatment into contact with an alkaline solution. Thus, the exposedportion of the composition layer is dissolved by the alkaline solutionand removed, and the unexposed portion of the composition layer remainson the substrate, whereby producing a resist pattern. Here, as thealkaline developing solution, various types of aqueous alkalinesolutions used in this field can be used. Examples include aqueoussolutions of tetramethylammonium hydroxide and(2-hydroxyethyl)trimethylammonium hydroxide (common name: choline).

After the development, it is preferable to rinse the substrate and thepattern with ultrapure water and to remove any residual water thereon.

<Application>

The resist composition of the present invention is useful as the resistcomposition for excimer laser lithography such as with ArF, KrF or thelike, and the resist composition for electron beam (EB) exposurelithography and extreme-ultraviolet (EUV) exposure lithography, as wellas liquid immersion exposure lithography.

The resist composition of the present invention can be used insemiconductor microfabrication and in manufacture of liquid crystals,thermal print heads for circuit boards and the like, and furthermore inother photofabrication processes, which can be suitably used in a widerange of applications.

EXAMPLES

The present invention will be described more specifically by way ofexamples, which are not construed to limit the scope of the presentinvention.

All percentages and parts expressing the content or amounts used in theExamples and Comparative Examples are based on weight, unless otherwisespecified.

The composition ratio of the resin (the copolymerization ratio of thestructural unit derived from each monomer used in the preparation withrespect to the resin) was calculated by measuring the amount of theunreacted monomer in the reacted solution after the completion of thereaction through liquid chromatography, and calculating the amount ofthe monomer use in the polymerization from the obtained results.

The weight average molecular weight is a value determined by gelpermeation chromatography.

Column: TSK gel Multipore HXL-M×3+guardcolumn (Tosoh Co. Ltd.)

Eluant: tetrahydrofuran

Flow rate: 1.0 mL/min

Detecting device: RI detector

Column temperature: 40° C.

Injection amount: 100 μL

Standard material for calculating molecular weight: standardpolysthylene (Toso Co. ltd.)

Synthesis Example 1 Synthesis of Compound Represented by the Formula (K)

10.00 parts of a compound (K-2), 40.00 parts of tetrahydrofuran and 7.29parts of pyridine were mixed, and stirred for 30 minutes at 23° C. Theobtained mixture was cooled to 0° C. To this mixture was added 33.08parts of a compound (K-1) over 1 hour while maintaining at the sametemperature. The temperature of the mixture was then elevated to about23° C., and the mixture was stirred for 3 hour at the same temperature.Thus obtained reactant was added to 361.51 parts of ethyl acetate and20.19 parts of 5% of hydrochloric acid solution to obtain a mixture, themixture was stirred for 30 minutes at 23° C. The obtained solution wasallowed to stand, and then separated to recover an organic layer. To therecovered organic layer, 81.42 parts of a saturated sodium hydrogencarbonate was added, and the obtained solution was stirred for 30minutes at 23° C., allowed to stand, and then separated to recover theorganic layer. To the recovered organic layer was added 90.38 parts ofion-exchanged water, and the obtained solution was stirred for 30minutes at 23° C., allowed to stand, and then separated to wash theorganic layer with water. These washing operations were repeated for 5times. The obtained organic layer was concentrated, resulting in 23.40parts of the compound (K).

MS (mass spectroscopy): 326.0 (molecular peak)

Synthesis Example 2 Synthesis of Compound Represented by the Formula (H)

88.00 parts of a compound (H-2), 616.00 parts of methyl isobutyl ketoneand 60.98 parts of pyridine were mixed, and stirred for 30 minutes at23° C. The obtained mixture was cooled to 0° C. To this mixture wasadded 199.17 parts of a compound (H-1) over 1 hour while maintaining atthe same temperature. The temperature of the mixture was then elevatedto about 10° C., and the mixture was stirred for 1 hour at the sametemperature. Thus obtained reactant was added to 1446.22 parts ofn-heptane and 703.41 parts of 2% of hydrochloric acid solution to obtaina mixture, the mixture was stirred for 30 minutes at 23° C. The obtainedsolution was allowed to stand, and then separated to recover an organiclayer. To the recovered organic layer, 337.64 parts of 2% ofhydrochloric acid solution was added to obtain a mixture, and themixture was stirred for 30 minutes at 23° C. The obtained solution wasallowed to stand, and then separated to recover an organic layer. To therecovered organic layer, 361.56 parts of ion-exchanged water was added,and the obtained solution was stirred for 30 minutes at 23° C., allowedto stand, and then separated to wash the organic layer with water. Tothe obtained organic layer, 443.92 parts of 10% of potassium carbonatewas added, and the obtained solution was stirred for 30 minutes at 23°C., allowed to stand, and then separated to recover the organic layer.These washing operations were repeated for 2 times. To the obtainedorganic layer, 361.56 parts of ion-exchanged water was added, and theobtained solution was stirred for 30 minutes at 23° C., allowed tostand, and then separated to wash the organic layer with water. Thesewashing operations were repeated for 5 times. The obtained organic layerwas concentrated, resulting in 163.65 parts of the compound (H).

MS (mass spectroscopy): 276.0 (molecular ion peak)

Synthesis Example 3 Synthesis of Compound Represented by the Formula (L)

30.00 parts of a compound (L-2), 210.00 parts of methyl isobutyl ketoneand 18.00 parts of pyridine were mixed, and stirred for 30 minutes at23° C. The obtained mixture was cooled to 0° C. To this mixture wasadded 48.50 parts of a compound (L-1) over 1 hour while maintaining atthe same temperature. The temperature of the mixture was then elevatedto about 5° C., and the mixture was stirred for 1 hour at the sametemperature. Thus obtained reactant was added to 630 parts of ethylacetate, 99.68 parts of 5% of hydrochloric acid solution and 126 partsof ion-exchanged water to obtain a mixture, the mixture was stirred for30 minutes at 23° C. The obtained solution was allowed to stand, andthen separated to recover an organic layer. To the recovered organiclayer, 86.50 parts of 10% of potassium carbonate solution was added toobtain a mixture, and the mixture was stirred for 30 minutes at 23° C.The obtained solution was allowed to stand, and then separated torecover an organic layer. These washing operations were repeated for twotimes. To the recovered organic layer, 157.50 parts of ion-exchangedwater was added, and the obtained solution was stirred for 30 minutes at23° C., allowed to stand, and then separated to wash the organic layerwith water. These washing operations were repeated for five times. Theobtained organic layer was concentrated, resulting in 27.61 parts of thecompound (L).

MS (mass spectroscopy): 354.1 (molecular ion peak)

Synthesis Example 4 Synthesis of Compound Represented by the Formula (M)

27.34 parts of a compound (M-2), 190.00 parts of methyl isobutyl ketoneand 18.00 parts of pyridine were mixed, and stirred for 30 minutes at23° C. The obtained mixture was cooled to 0° C. To this mixture wasadded 48.50 parts of a compound (M-1) over 1 hour while maintaining atthe same temperature. The temperature of the mixture was then elevatedto about 5° C., and the mixture was stirred for 1 hour at the sametemperature. Thus obtained reactant was added to 570 parts of ethylacetate, 99.68 parts of 5% of hydrochloric acid solution and 126 partsof ion-exchanged water to obtain a mixture, the mixture was stirred for30 minutes at 23° C. The obtained solution was allowed to stand, andthen separated to recover an organic layer. To the recovered organiclayer, 86.50 parts of 10% of potassium carbonate solution was added toobtain a mixture, and the mixture was stirred for 30 minutes at 23° C.The obtained solution was allowed to stand, and then separated torecover an organic layer. These washing operations were repeated for twotimes. To the recovered organic layer, 150 parts of ion-exchanged waterwas added, and the obtained solution was stirred for 30 minutes at 23°C., allowed to stand, and then separated to wash the organic layer withwater. These washing operations were repeated for five times. Theobtained organic layer was concentrated, resulting in 23.89 parts of thecompound (M).

MS (mass spectroscopy): 340.1 (molecular ion peak)

Synthetic Example of the Resin

The monomers used the synthesis of the resin are shown below.

These monomers are referred to as “monomer (A)” to “monomer (N)”.

Synthetic Example 5 Synthesis of Resin A1-1

Monomer (H) was used, and dioxane was added thereto in an amount equalto 1.5 times by weight of the total amount of monomers to obtain asolution. Azobisisobutyronitrile and azobis(2,4-dimethylvaleronitrile)was added as an initiator to obtain a solution in an amount of 0.7 mol %and 2.1 mol % respectively with respect to the entire amount ofmonomers, and the resultant mixture was heated for about 5 hours at 75°C. After that, the obtained reacted mixture was poured into a largeamount of methanol/water mixed solvent to precipitate a resin. Thusobtained resin was filtrated, and dissolved in another dioxane to obtaina solution, and the solution was poured into a mixture of methanol/watermixed solvent to precipitate a resin. The obtained resin was filtrated.These operations were repeated for two times, resulting in a 77% yieldof copolymer having a weight average molecular weight of about 18000.This copolymer, which had the structural units of the following formula,was referred to Resin A1-1.

Synthetic Example 6 Synthesis of Resin A1-2

Monomer (K) and monomer (I) were mixed together with a mole ratio ofMonomer (K):monomer (I)=90:10, and dioxane was added thereto in anamount equal to 1.5 times by weight of the total amount of monomers toobtain a solution. Azobisisobutyronitrile andazobis(2,4-dimethylvaleronitrile) was added as an initiator to obtain asolution in an amount of 1 mol % and 3 mol % respectively with respectto the entire amount of monomers, and the resultant mixture was heatedfor about 5 hours at 72° C. After that, the obtained reacted mixture waspoured into a large amount of n-heptane to precipitate a resin. Theobtained resin was filtrated, resulting in a 70% yield of copolymerhaving a weight average molecular weight of about 13000. This copolymer,which had the structural units of the following formula, was referred toResin A1-2.

Synthetic Example 7 Synthesis of Resin A1-3

Monomer (L) was used, and dioxane was added thereto in an amount equalto 1.5 times by weight of the total amount of monomers to obtain asolution. Azobisisobutyronitrile and azobis(2,4-dimethylvaleronitrile)was added as an initiator to obtain a solution in an amount of 0.7 mol %and 2.1 mol % respectively with respect to the entire amount ofmonomers, and the resultant mixture was heated for about 5 hours at 75°C. After that, the obtained reacted mixture was poured into a largeamount of methanol/water mixed solvent to precipitate a resin. Thusobtained resin was dissolved in another dioxane to obtain a solution,and the solution was poured into a mixture of methanol/water mixedsolvent to precipitate a resin. The obtained resin was filtrated. Theseoperations were repeated for two times, resulting in a 73% yield ofcopolymer having a weight average molecular weight of about 19000. Thiscopolymer, which had the structural units of the following formula, wasreferred to Resin A1-3.

Synthetic Example 8 Synthesis of Resin A1-4

Monomer (M) was used, and dioxane was added thereto in an amount equalto 1.5 times by weight of the total amount of monomers to obtain asolution. Azobisisobutyronitrile and azobis(2,4-dimethylvaleronitrile)was added as an initiator to obtain a solution in an amount of 0.7 mol %and 2.1 mol % respectively with respect to the entire amount ofmonomers, and the resultant mixture was heated for about 5 hours at 75°C. After that, the obtained reacted mixture was poured into a largeamount of methanol/water mixed solvent to precipitate a resin. Thusobtained resin was dissolved in another dioxane to obtain a solution,and the solution was poured into a mixture of methanol/water mixedsolvent to precipitate a resin. The obtained resin was filtrated. Theseoperations were repeated for two times, resulting in a 76% yield ofcopolymer having a weight average molecular weight of about 18000. Thiscopolymer, which had the structural units of the following formula, wasreferred to Resin A1-4.

Synthetic Example 9 Synthesis of Resin A2-1

Monomer (D), monomer (E), monomer (B), monomer (C) and monomer (F) weremixed together with a mole ratio of monomer (D):monomer (E):monomer(B):monomer (C):monomer (F)=30:14:6:20:30, and dioxane was added theretoin an amount equal to 1.5 times by weight of the total amount ofmonomers to obtain a solution. Azobisisobutyronitrile andazobis(2,4-dimethylvaleronitrile) was added as an initiator to obtain asolution in an amount of 1 mol % and 3 mol % respectively with respectto the entire amount of monomers, and the resultant mixture was heatedfor about 5 hours at 73° C. After that, the obtained reacted mixture waspoured into a mixture of a large amount of methanol and water(methanol:water=4:1, weight ratio) to precipitate a resin. The obtainedresin was filtrated. Thus obtained resin was dissolved in anotherdioxane to obtain a solution, and the solution was poured into a largeamount of a mixture of methanol and water to precipitate a resin. Theobtained resin was filtrated. These operations were repeated two times,resulting in a 65% yield of copolymer having a weight average molecularweight of about 8100. This copolymer, which had the structural units ofthe following formula, was referred to Resin A2-1.

Synthetic Example 10 Synthesis of Resin A2-2

Monomer (A), monomer (E), monomer (B), monomer (C) and monomer (F) weremixed together with a mole ratio of monomer (A):monomer (E):monomer(B):monomer (C):monomer (F)=30:14:6:20:30, and dioxane was added theretoin an amount equal to 1.5 times by weight of the total amount ofmonomers to obtain a solution. Azobisisobutyronitrile andazobis(2,4-dimethylvaleronitrile) was added as an initiator to obtain asolution in an amount of 1 mol % and 3 mol % respectively with respectto the entire amount of monomers, and the resultant mixture was heatedfor about 5 hours at 73° C. After that, the obtained reacted mixture waspoured into a mixture of a large amount of methanol and water(methanol:water=4:1, weight ratio) to precipitate a resin. The obtainedresin was filtrated. Thus obtained resin was dissolved in anotherdioxane to obtain a solution, and the solution was poured into a largeamount of a mixture of methanol and water to precipitate a resin. Theobtained resin was filtrated. These operations were repeated two times,resulting in a 68% yield of copolymer having a weight average molecularweight of about 7800. This copolymer, which had the structural units ofthe following formula, was referred to Resin A2-2.

Synthetic Example 11 Synthesis of Resin A2-3

Monomer (A), monomer (B) and monomer (C) were mixed together with a moleratio of monomer (A):monomer (B): monomer (C)=50:25:25, and dioxane wasadded thereto in an amount equal to 1.5 times by weight of the totalamount of monomers to obtain a solution. Azobisisobutyronitrile andazobis(2,4-dimethylvaleronitrile) was added as an initiator to obtain asolution in an amount of 1.0 mol % and 3.0 mol % respectively withrespect to the entire amount of monomers, and the resultant mixture washeated for about 8 hours at 80° C. After that, the obtained reactedmixture was poured into a mixture of a large amount of methanol andwater (methanol:water=4:1, weight ratio) to precipitate a resin. Theobtained resin was filtrated. Thus obtained resin was dissolved inanother dioxane to obtain a solution, and the solution was poured into amixture of methanol and water to precipitate a resin. The obtained resinwas filtrated. These operations were repeated three times, resulting ina 60% yield of copolymer having a weight average molecular weight ofabout 9200. This copolymer, which had the structural units of thefollowing formula, was referred to Resin A2-3.

Synthetic Example 12 Synthesis of Resin A2-4

Monomer (A), monomer (E), monomer (B), monomer (F) and monomer (C) weremixed together with a mole ratio of monomer (A):monomer (E):monomer(B):monomer (F):monomer (C)=30:14:6:20:30, and dioxane was added theretoin an amount equal to 1.5 times by weight of the total amount ofmonomers to obtain a solution. Azobisisobutyronitrile andazobis(2,4-dimethylvaleronitrile) was added as an initiator to obtain asolution in an amount of 1 mol % and 3 mol % respectively with respectto the entire amount of monomers, and the resultant mixture was heatedfor about 5 hours at 75° C. After that, the obtained reacted mixture waspoured into a mixture of a large amount of methanol and water toprecipitate a resin. The obtained resin was filtrated. Thus obtainedresin was dissolved in another dioxane to obtain a solution, and thesolution was poured into a large amount of a mixture of methanol andwater to precipitate a resin. The obtained resin was filtrated. Theseoperations were repeated two times, resulting in a 78% yield ofcopolymer having a weight average molecular weight of about 7200. Thiscopolymer, which had the structural units of the following formula, wasreferred to Resin A2-4.

Synthetic Example 13 Synthesis of Resin A2-5

Monomer (A), monomer (N), monomer (B), monomer (F) and monomer (C) weremixed together with a mole ratio of monomer (A):monomer (N):monomer(B):monomer (F):monomer (C)=30:14:6:20:30, and dioxane was added theretoin an amount equal to 1.5 times by weight of the total amount ofmonomers to obtain a solution. Azobisisobutyronitrile andazobis(2,4-dimethylvaleronitrile) was added as an initiator to obtain asolution in an amount of 1 mol % and 3 mol % respectively with respectto the entire amount of monomers, and the resultant mixture was heatedfor about 5 hours at 75° C. After that, the obtained reacted mixture waspoured into a mixture of a large amount of methanol and water toprecipitate a resin. The obtained resin was filtrated. Thus obtainedresin was dissolved in another dioxane to obtain a solution, and thesolution was poured into a large amount of a mixture of methanol andwater to precipitate a resin. The obtained resin was filtrated. Theseoperations were repeated two times, resulting in a 78% yield ofcopolymer having a weight average molecular weight of about 7200. Thiscopolymer, which had the structural units of the following formula, wasreferred to Resin A2-5.

Synthetic Example 14 Synthesis of Resin X1

Monomer (G), monomer (C) and monomer (B) were mixed together with a moleratio of monomer (G):monomer (C):monomer (B)=35:45:20, and dioxane wasadded thereto in an amount equal to 1.5 times by weight of the totalamount of monomers to obtain a solution. Azobisisobutyronitrile andazobis(2,4-dimethylvaleronitrile) was added as an initiator to obtain asolution in an amount of 1.0 mol % and 3.0 mol % respectively withrespect to the entire amount of monomers, and the resultant mixture washeated for about 5 hours at 75° C. After that, the obtained reactedmixture was poured into a mixture of a large amount of methanol andwater to precipitate a resin. The obtained resin was filtrated. Thusobtained resin was dissolved in another dioxane to obtain a solution,and the solution was poured into a mixture of methanol and water toprecipitate a resin. The obtained resin was filtrated. These operationswere repeated 2 times, resulting in a 75% yield of copolymer having aweight average molecular weight of about 7000. This copolymer, which hadthe structural units of the following formula, was referred to Resin X1.The mole ratio of each structural unit is structural unit (G):structuralunit (C):structural unit (B)=34.7:45.4:19.9.

Synthetic Example 15 Synthesis of Resin X2

Monomer (J) and monomer (G) were mixed together with a mole ratio ofmonomer (J):monomer (G)=80:20, and dioxane was added thereto in anamount equal to 1.5 times by weight of the total amount of monomers toobtain a solution. Azobisisobutyronitrile andazobis(2,4-dimethylvaleronitrile) was added as an initiator to obtain asolution in an amount of 0.5 mol % and 1.5 mol % respectively withrespect to the entire amount of monomers, and the resultant mixture washeated for about 5 hours at 70° C. After that, the obtained reactedmixture was poured into a mixture of a large amount of methanol andwater to precipitate a resin. The obtained resin was filtrated. Thusobtained resin was dissolved in another dioxane to obtain a solution,and the solution was poured into a mixture of methanol and ion-exchangedwater to precipitate a resin. The obtained resin was filtrated. Theseoperations were repeated 2 times, resulting in a 70% yield of copolymerhaving a weight average molecular weight of about 28000. This copolymer,which had the structural units of the following formula, was referred toResin X2. The mole ratio of each structural unit is structural unit(J):structural unit (G)=80.2:19.8.

(Preparing Resist Composition)

Resist compositions were prepared by mixing and dissolving each of thecomponents shown in Table 1, and then filtrating through a fluororesinfilter having 0.2 μm pore diameter.

TABLE 1 (Unit: parts) Acid Compound BP/PEB Resin Generator (II) (° C./°C.) Ex. 1 A1-1/A2-1 = 0.7/10 B1 = 1.4 I1 = 0.1 95/85 2 A1-1/A2-2 =0.7/10 B1 = 1.4 I1 = 0.1 110/105 3 A1-2/A2-1 = 0.3/10 B1 = 1.4 I1 = 0.195/85 4 A1-2/A2-2 = 0.3/10 B1 = 1.4 I1 = 0.1 110/105 5 A1-1/A2-3 =0.7/10 B1 = 1.4 I1 = 0.1 110/105 6 A1-1/A2-2 = 0.7/10 B2/B3 = I1 = 0.1110/105 1.0/0.1 7 A1-1/A2-4 = 0.7/10 B1 = 1.4 I1 = 0.1 110/105 8A1-1/A2-5 = 0.7/10 B1 = 1.4 I1 = 0.1 110/105 9 A1-3/A2-5 = 0.7/10 B1 =1.4 I1 = 0.1 110/105 10  A1-4/A2-5 = 0.7/10 B1 = 1.4 I1 = 0.1 110/105Comparative Ex. 1 X2/X1 = 0.3/10 B2/B3 = — 110/105 1.0/0.1<Resin>

Resins prepared by the Synthetic Examples

<Acid Generator>

B1: this was prepared by a method according to the method described inthe Examples of JP2010-152341A

B2: this was prepared by a method according to the method described inthe Examples of WO2008/99869 and JP2010-26478A

B3: this was prepared by a method according to the method described inthe Examples of JP2005-221721A

<Basic Compound: Qencher>

C1: 2,6-diisopropylaniline (obtained from Tokyo Chemical Industry Co.,LTD)

<Compound (II)>

I1: obtained from Tokyo Chemical Industry Co., LTD

<Solvent of Resist Composition>

Propylene glycol monomethyl ether acetate 265 parts  Propylene glycolmonomethyl ether 20 parts 2-Heptanone 20 parts γ-butyrolactone 3.5parts (Producing Resist Pattern)

A composition for an organic antireflective film (“ARC-29”, by NissanChemical Co. Ltd.) was applied onto 12-inch silicon wafers and baked for60 seconds at 205° C. to form a 78 nm thick organic antireflective film.

The above resist compositions were then applied thereon by spin coatingso that the thickness of the resulting film became 85 nm after drying.

The obtained wafers were then pre-baked for 60 sec on a direct hot plateat the temperatures given in the “PB” column in Table 1 to obtain acomposition layer.

Line and space patterns were then exposed through stepwise changes inexposure quantity using an ArF excimer stepper for immersion lithography(“XT:1900Gi” by ASML Ltd.: NA=1.35, 3/4 Annular, X-Y deflection), on thewafers on which the composition layer thus been formed.

The exposure was followed by 60 seconds of post-exposure baking at thetemperatures given in the “PEB” column in Table 1.

This was followed by 60 sec of puddle development with 2.38 wt %tetramethylammonium hydroxide aqueous solution to obtain a resistpattern.

Effective sensitivity was represented as the exposure amount at which a50 nm line and space pattern resolved to 1:1 with the each resist film.

(Line Edge Roughness (LER) Evaluation)

When the wall surface of the resist pattern following the lithographyprocess was observed using a scanning electron microscope,

a “∘∘” on was given if the irregularity in the resist pattern side wallhave a roughness width ≦4 nm,

a “∘” was given when the roughness width was >4 nm and ≦4.5 nm, and

an “x” was given when the roughness width was <4.5 nm.

Table 2 illustrates there results. The parenthetical number meansroughness width values.

(Evaluation of Defects)

The above resist compositions were applied on each of the12-inch-silicon wafers by spin coating so that the thickness of theresulting film became 150 nm after drying.

The obtained wafers were then pre-baked for 60 seconds on a direct hotplate at the temperatures given in the “PB” column in Table 3 to obtaina composition layer.

The thus obtained wafers with the produced composition layers wererinsed with water for 60 seconds using a developing apparatus (ACT-12,Tokyo electron Co. Ltd.).

Thereafter, the number of defects was counted using a defect inspectionapparatus (KLA-2360, KLA-Tencor Co. Ltd.)

Table 2 illustrates there results.

TABLE 2 Ex. LER Defects 1 ∘∘(3.12) 160 2 ∘∘(3.28) 190 3 ∘∘(3.68) 240 4∘∘(3.84) 280 5   ∘(4.02) 290 6 ∘∘(3.40) 250 7 ∘∘(3.24) 170 8 ∘∘(3.20)150 9 ∘∘(3.42) 120 10  ∘∘(3.36) 140 Comp. Ex. 1   x(5.68) 720

According to the resist composition of the present invention, it ispossible to achieve satisfactory wide focus margin (DOF) and defect-freein the obtained resist pattern. Therefore, the present resistcomposition can be used for semiconductor microfabrication.

What is claimed is:
 1. A resist composition comprising (A1) a resinhaving a structural unit represented by the formula (I), (A2) a resinbeing insoluble or poorly soluble in alkali aqueous solution, butbecoming soluble in an alkali aqueous solution by the action of an acid,(B) an acid generator and (D) a compound represented by the formula(II),

wherein R¹ represents a hydrogen atom or a methyl group; A¹ represents aC₁ to C₆ alkanediyl group; R² represents a C₁ to C₁₀ hydrocarbon grouphaving a fluorine atom;

wherein R³ and R⁴ in each occurrence independently represent a C₁ to C₁₂hydrocarbon group, a C₁ to C₆ alkoxyl group, a C₂ to C₇ acyl group, a C₂to C₇ acyloxy group, a C₂ to C₇ alkoxycarbonyl group, a nitro group or ahalogen atom; m′ and n′ independently represent an integer of 0 to
 4. 2.The resist composition according to claim 1, wherein R² in the formula(I) is a C₁ to C₆ fluorinated alkyl group.
 3. The resist compositionaccording to claim 1, wherein A¹ in the formula (I) is a C₂ to C₄alkanediyl group.
 4. The resist composition according to claim 3,wherein A¹ in the formula (I) is an ethylene group.
 5. The resistcomposition according to claim 1, which further comprises a solvent. 6.A method for producing resist pattern comprising steps of; (1) applyingthe resist composition of claim 1 onto a substrate; (2) drying theapplied composition to form a composition layer; (3) exposing thecomposition layer; (4) heating the exposed composition layer, and (5)developing the heated composition layer.